Multi-part energizer for mechanical seal assembly

Abstract

An energizer for a mechanical seal assembly for use in a drill bit is disclosed. The energizer is a composite of at least two resilient materials, one having a durometer hardness that is greater than the other. The material contacting a journal provides relatively high frictional forces so as to prevent the energizer from rotating in relation to adjacent components. The relatively softer resilient material provides the energizing force necessary to maintain a good dynamic seal between the metal seal rings. The energizer components may be separate components that engage one another upon assembly, or may be bonded together to form a ring prior to assembly into the drill bit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not Applicable. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The invention relates generally to seal assemblies for sealing between a rotating and a static member. In one aspect, and more particularly, the invention relates to seals for rolling cone bits used to drill a borehole for the ultimate recovery of oil, gas or minerals. Still more particularly, the invention relates to energizers for mechanical face, metal-to-metal seals that are employed to seal and protect the bearing surfaces between the rolling cone cutters and the journal shafts on which they rotate. [0005] 2. Description of the Related Art [0006] An earth-boring drill bit is typically mounted on the lower end of a drill string. With weight applied to the drill string, the drill string is rotated such that the bit engages the earthen formation and proceeds to form ...

AI Technical Summary

Benefits of technology

[0023] The use of materials having differing hardnesses, and optimizing the shape and hardness of the various components of the energizer offer the ability to enhance frictional forces to ensure that the energizer does not rotate, but instead remains static with respect to the drill bit body and the substantially rigid seal ring so as to enhance life of the energizer and enhance the effectiveness of the seal. Collectively, these features may offer the ability to increase the life of the seal and thus enhance bit life, thereby advancing the state of the art.

Problems solved by technology

When cuttings are conveyed into the seal gland, they tend to adhere to the gland and / or seal component surfaces, and may cause deformation, damage and / or slippage of the seal components.

Moreover, the cuttings can accelerate abrasive wear of all seal components and of the bearing surfaces.

The amount of time required to make a round trip for replacing a bit is essentially lost from drilling operations.

As is thus obvious, this process, known as a “trip” of the drill string, requires considerable time, effort and expense.

Importantly, the seals must function for substantial periods under extremely harsh downhole conditions.

One cause of bit failure arises from the severe wear or damage that may occur to the bearings on which the cone cutters are mounted.

These bearings can be friction bearings (also referred to as journal bearings) or roller type bearings, and are typically subjected to high drilling loads, high hydrostatic pressures, and high temperatures.

One of the failure modes for mechanical seals is undesirable energizer rotation.

Unfortunately, once an energizer begins to rotate, it wears away quickly, resulting in loss of lubricant from the bearing surfaces or the ingress of abrasive drilling fluid and / or drilled cuttings into the bearing region since a pressure difference exists on two sides of the energizer.

As a result of either or both of these conditions, the mechanical seals will prematurely fail, leading ultimately to bit failure and the need to “trip” the drill string in order to replace the failed bit.

However, each of these techniques is time consuming and thus adds additional cost and time to manufacturing the drill bit.

Further, roughening the contact surfaces is not entirely reliable, and in certain instances, it cannot provide sufficient friction to prevent the energizer from rotating.

Further still, once some energizer rotation has occurred, the roughened surface abrades the engaged energizer surface, and thereby accelerates the wear and deterioration of the energizer.

Thus, the proposed solution to seal failure caused by undesirable energizer rotation may, in certain instances, actually exacerbates the problem and leads to energizer deterioration and seal failure earlier than would otherwise occur.

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